This photo provided by KFOR-TV shows a house fire outside Moore, Okla., Monday, May 20, 2013. A monstrous tornado as much as a mile wide roared through the Oklahoma City suburbs Monday, flattening entire neighborhoods, setting buildings on fire and landing a direct blow on an elementary school. (AP Photo/KFOR-TV) less

This photo provided by KFOR-TV shows a house fire outside Moore, Okla., Monday, May 20, 2013. A monstrous tornado as much as a mile wide roared through the Oklahoma City suburbs Monday, flattening entire ... more

This photo provided by KFOR-TV shows a house fire outside Moore, Okla., Monday, May 20, 2013. A monstrous tornado as much as a mile wide roared through the Oklahoma City suburbs Monday, flattening entire neighborhoods, setting buildings on fire and landing a direct blow on an elementary school. (AP Photo/KFOR-TV) less

This photo provided by KFOR-TV shows a house fire outside Moore, Okla., Monday, May 20, 2013. A monstrous tornado as much as a mile wide roared through the Oklahoma City suburbs Monday, flattening entire ... more

This photo provided by KFOR-TV shows homes flattened outside Moore, Okla., Monday, May 20, 2013. A monstrous tornado as much as a mile wide roared through the Oklahoma City suburbs Monday, flattening entire neighborhoods, setting buildings on fire and landing a direct blow on an elementary school. (AP Photo/KFOR-TV) MANDATORY CREDIT less

This photo provided by KFOR-TV shows homes flattened outside Moore, Okla., Monday, May 20, 2013. A monstrous tornado as much as a mile wide roared through the Oklahoma City suburbs Monday, flattening entire ... more

A woman carries her child through a field near the collapsed Plaza Towers Elementary School in Moore, Okla., Monday, May 20, 2013. A tornado as much as a mile (1.6 kilometers) wide with winds up to 200 mph (320 kph) roared through the Oklahoma City suburbs Monday, flattening entire neighborhoods, setting buildings on fire and landing a direct blow on an elementary school. (AP Photo Sue Ogrocki) less

A woman carries her child through a field near the collapsed Plaza Towers Elementary School in Moore, Okla., Monday, May 20, 2013. A tornado as much as a mile (1.6 kilometers) wide with winds up to 200 mph (320 ... more

Photo: Sue Ogrocki, Associated Press

A woman carries her child through a field near the collapsed Plaza... Photo-4656846.62754 - Houston Chronicle

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This photo provided by KFOR-TV shows a car pile-up outside Moore, Okla., Monday, May 20, 2013. A monstrous tornado as much as a mile wide roared through the Oklahoma City suburbs Monday, flattening entire neighborhoods, setting buildings on fire and landing a direct blow on an elementary school. (AP Photo/KFOR-TV) less

This photo provided by KFOR-TV shows a car pile-up outside Moore, Okla., Monday, May 20, 2013. A monstrous tornado as much as a mile wide roared through the Oklahoma City suburbs Monday, flattening entire ... more

This frame grab provided by KWTV shows a tornato in Oklahoma City Monday, April 20, 2013. Television footage shows flattened buildings and fires after a mile-wide tornado moved through the Oklahoma City area. (AP Photo/Courtesy KWTV) less

This frame grab provided by KWTV shows a tornato in Oklahoma City Monday, April 20, 2013. Television footage shows flattened buildings and fires after a mile-wide tornado moved through the Oklahoma City area. ... more

This frame grab provided by KWTV shows a tornato in Oklahoma City Monday, April 20, 2013. Television footage shows flattened buildings and fires after a mile-wide tornado moved through the Oklahoma City area. (AP Photo/Courtesy KWTV) less

This frame grab provided by KWTV shows a tornato in Oklahoma City Monday, April 20, 2013. Television footage shows flattened buildings and fires after a mile-wide tornado moved through the Oklahoma City area. ... more

A resident who did not want to give his name, searches through the rubble of his mobile home in the Steelman Estates Mobile Home Park, destroyed by Sunday's tornado, near Shawnee, Okla., Monday, May 20, 2013. The tornado that slammed into Oklahoma on Sunday is now blamed for two deaths. Authorities say two men in their 70s have been found dead in or near a mobile home park outside of Shawnee. (AP Photo Sue Ogrocki) less

A resident who did not want to give his name, searches through the rubble of his mobile home in the Steelman Estates Mobile Home Park, destroyed by Sunday's tornado, near Shawnee, Okla., Monday, May 20, 2013. ... more

Photo: Sue Ogrocki, Associated Press

A resident who did not want to give his name, searches through the... Photo-4656381.62754 - Houston Chronicle

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Maeghan Hadley, of One Day Ranch pet rescue, checks over a kitten pulled from under the rubble of a mobile home destroyed by Sunday's tornado in the Steelman Estates Mobile Home Park, near Shawnee, Okla., Monday, May 20, 2013. (AP Photo Sue Ogrocki) less

Maeghan Hadley, of One Day Ranch pet rescue, checks over a kitten pulled from under the rubble of a mobile home destroyed by Sunday's tornado in the Steelman Estates Mobile Home Park, near Shawnee, Okla., ... more

Photo: Sue Ogrocki, Associated Press

Maeghan Hadley, of One Day Ranch pet rescue, checks over a kitten... Photo-4656388.62754 - Houston Chronicle

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This photograph obtained courtesy of KFOR-TV in Oklahoma City, Oklahoma shows emergency crews searching amid destruction May 19, 2013 after a tornado ripped through Twin Lakes, Oklahoma. Tornadoes damaged many areas across the West South Central US state of Oklahoma. AFP PHOTO / KFOR-TV == RESTRICTED TO EDITORIAL USE / MANDATORY CREDIT: "AFP PHOTO / KFOR-TV "/ NO SALES / NO MARKETING / NO ADVERTISING CAMPAIGNS / DISTRIBUTED AS A SERVICE TO CLIENTS ==-/AFP/Getty Images less

Seven-year-old Katrina Ash, left, watches with her mother, Amber Ash, right, as heavy equipment is brought into their tornado damaged neighborhood near Dale, Okla., Sunday, May 19, 2013. Residents are not being allowed into the neighborhood as search and rescue operations continue. (AP Photo Sue Ogrocki) less

Seven-year-old Katrina Ash, left, watches with her mother, Amber Ash, right, as heavy equipment is brought into their tornado damaged neighborhood near Dale, Okla., Sunday, May 19, 2013. Residents are not being ... more

Seven-year-old Katrina Ash, right, holds a doll as she waits in the back of a truck with her grandfather, Michael Bowen, left, after a tornado ripped through their neighborhood near Dale, Okla., Sunday, May 19, 2013. Residents are not being allowed back into the neighborhood as search and rescue efforts take place. (AP Photo Sue Ogrocki) less

Seven-year-old Katrina Ash, right, holds a doll as she waits in the back of a truck with her grandfather, Michael Bowen, left, after a tornado ripped through their neighborhood near Dale, Okla., Sunday, May 19, ... more

June McFarland reacts to the first sight of storm damage in rural Osage, Iowa on Sunday, May 19, 2013. A powerful weather system moved through the area on Sunday afternoon triggering tornado warnings, high winds and hail. (AP Photo/The Globe Gazette, Arian Schuessler) less

June McFarland reacts to the first sight of storm damage in rural Osage, Iowa on Sunday, May 19, 2013. A powerful weather system moved through the area on Sunday afternoon triggering tornado warnings, high ... more

Photo: Arian Schuessler, Associated Press

June McFarland reacts to the first sight of storm damage in rural... Photo-4652773.62754 - Houston Chronicle

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Seven-year-old Katrina Ash, right, holds a doll as she waits with her grandfather, Michael Bowen, left, after a tornado ripped through their neighborhood near Dale, Okla., Sunday, May 19, 2013. Residents are not being allowed back into the neighborhood as search and rescue efforts take place. (AP Photo Sue Ogrocki) less

Seven-year-old Katrina Ash, right, holds a doll as she waits with her grandfather, Michael Bowen, left, after a tornado ripped through their neighborhood near Dale, Okla., Sunday, May 19, 2013. Residents are ... more

Residents of Edmond, Okla., survey storm damage from a tornado that hit their neighborhood Sunday, May 19, 2013. Forecasters had warned that the middle of the country would see severe weather throughout the weekend. (AP Photo/Sean Murphy) less

Residents of Edmond, Okla., survey storm damage from a tornado that hit their neighborhood Sunday, May 19, 2013. Forecasters had warned that the middle of the country would see severe weather throughout the ... more

Jerry Dirks, at right, hugs her friend Earlene Langley after a tornado hit Driks' home just south of Carney Okla., on Sunday, May 19, 2013. Dirks was in her cellar at the time the tornado hit. (AP Photo/The Oklahoman, Bryan Terry) less

Jerry Dirks, at right, hugs her friend Earlene Langley after a tornado hit Driks' home just south of Carney Okla., on Sunday, May 19, 2013. Dirks was in her cellar at the time the tornado hit. (AP Photo/The ... more

Friends and neighbors help out a resident in Lyon County just south of Emporia, Kan., Sunday evening, May 19, 2013 after an apparent tornado touched down. (AP Photo/Emporia Gazette, Matthew Fowler)

Friends and neighbors help out a resident in Lyon County just south of Emporia, Kan., Sunday evening, May 19, 2013 after an apparent tornado touched down. (AP Photo/Emporia Gazette, Matthew Fowler)

Photo: Matthew Fowler, Associated Press

Friends and neighbors help out a resident in Lyon County just south... Photo-4652779.62754 - Houston Chronicle

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Damaged structures are seen May 19, 2013 after a tornado ripped through Wellston, Oklahoma. Tornadoes damaged many areas across the state May 19, 2013 and are still forming. Homes have been destroyed, with the worst damage so far just outside of Wellston. AFP PHOTO / KFOR-TV == RESTRICTED TO EDITORIAL USE / MANDATORY CREDIT: "AFP PHOTO / KFOR-TV "/ NO SALES / NO MARKETING / NO ADVERTISING CAMPAIGNS / DISTRIBUTED AS A SERVICE TO CLIENTS ==
-/AFP/Getty Images less

Damaged structures are seen May 19, 2013 after a tornado ripped through Wellston, Oklahoma. Tornadoes damaged many areas across the state May 19, 2013 and are still forming. Homes have been destroyed, with the ... more

Photo: -, AFP/Getty Images

Damaged structures are seen May 19, 2013 after a tornado ripped... Photo-4652786.62754 - Houston Chronicle

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People survey damage from a tornado that hit Edmond, Okla., on Sunday, May 19, 2013. A powerful storm system rumbled through the Plains and upper Midwest on Sunday, spawning tornadoes that damaged roofs and structures near Oklahoma City and kicked up debris in Wichita, Kan. (AP Photo/Sean Murphy) less

People survey damage from a tornado that hit Edmond, Okla., on Sunday, May 19, 2013. A powerful storm system rumbled through the Plains and upper Midwest on Sunday, spawning tornadoes that damaged roofs and ... more

This imaged obtained courtesy of KFOR-TV shows damaged structures on May 19, 2013 after a tornado ripped through Wellston, Oklahoma. Tornadoes damaged many areas across the state May 19, 2013 and are still forming. Homes have been destroyed, with the worst damage so far just outside of Wellston. AFP PHOTO / KFOR-TV == RESTRICTED TO EDITORIAL USE / MANDATORY CREDIT: "AFP PHOTO / KFOR-TV "/ NO SALES / NO MARKETING / NO ADVERTISING CAMPAIGNS / DISTRIBUTED AS A SERVICE TO CLIENTS ==-/AFP/Getty Images less

This imaged obtained courtesy of KFOR-TV shows damaged structures on May 19, 2013 after a tornado ripped through Wellston, Oklahoma. Tornadoes damaged many areas across the state May 19, 2013 and are still ... more

Marlena Hodson walks out of her home as her grandsons, Campbell Miller, 10, and Dillon Miller, 13, at right, help her sort through belongings after a tornado damaged her home Carney Okla., on Sunday, May 19, 2013. Hodson and her family left the home to escape the tornado. less

Marlena Hodson walks out of her home as her grandsons, Campbell Miller, 10, and Dillon Miller, 13, at right, help her sort through belongings after a tornado damaged her home Carney Okla., on Sunday, May 19, ... more

Photo: The Oklahoman, Bryan Terry

Marlena Hodson walks out of her home as her grandsons, Campbell... Photo-4653691.62754 - Houston Chronicle

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Nancy and Jason Townsend sort through belongings after their home was hit by a tornado in Carney Okla., on Sunday, May 19, 2013. The Townsend's left their home to avoid the tornado.

Nancy and Jason Townsend sort through belongings after their home was hit by a tornado in Carney Okla., on Sunday, May 19, 2013. The Townsend's left their home to avoid the tornado.

A flag flies in the debris of a mobile home after a tornado struck a mobile home park near Dale, Okla., Sunday, May 19, 2013.

A flag flies in the debris of a mobile home after a tornado struck a mobile home park near Dale, Okla., Sunday, May 19, 2013.

Photo: AP

A flag flies in the debris of a mobile home after a tornado struck... Photo-4653689.62754 - Houston Chronicle

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Damaged homes are seen in Carney, Okla., on Sunday, May 19, 2013, after a tornado moved through the area.Damaged homes are seen in Carney, Okla., on Sunday, May 19, 2013, after a tornado moved through the area.

Damaged homes are seen in Carney, Okla., on Sunday, May 19, 2013, after a tornado moved through the area.Damaged homes are seen in Carney, Okla., on Sunday, May 19, 2013, after a tornado moved through the area.

Photo: The Oklahoman, Bryan Terry

Damaged homes are seen in Carney, Okla., on Sunday, May 19, 2013,... Photo-4653687.62754 - Houston Chronicle

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Debris is scattered in what was a mobile home park where a tornado struck near Dale, Okla., Sunday, May 19, 2013.

Debris is scattered in what was a mobile home park where a tornado struck near Dale, Okla., Sunday, May 19, 2013.

Photo: AP

Debris is scattered in what was a mobile home park where a tornado... Photo-4653685.62754 - Houston Chronicle

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The frame of a mobile home is pictured with debris after a tornado hit a mobile home park near Dale, Okla., Sunday, May 19, 2013.

The frame of a mobile home is pictured with debris after a tornado hit a mobile home park near Dale, Okla., Sunday, May 19, 2013.

Photo: AP

The frame of a mobile home is pictured with debris after a tornado... Photo-4653683.62754 - Houston Chronicle

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Alli Christian, left, returns Jessica Wilkinson's dog Bella to her after finding her among the wreckage of Wilkinson's home shortly after a tornado struck near 156th street and Franklin Road on Sunday, May 19, 2013 in Norman, Okla. No one was in the home when the storm struck. less

Alli Christian, left, returns Jessica Wilkinson's dog Bella to her after finding her among the wreckage of Wilkinson's home shortly after a tornado struck near 156th street and Franklin Road on Sunday, May 19, ... more

John Warner surveys the damage near a friend's mobile home in the Steelman Estates Mobile Home Park, destroyed in Sunday's tornado, near Shawnee, Okla., Monday, May 20, 2013. (AP Photo Sue Ogrocki)

John Warner surveys the damage near a friend's mobile home in the Steelman Estates Mobile Home Park, destroyed in Sunday's tornado, near Shawnee, Okla., Monday, May 20, 2013. (AP Photo Sue Ogrocki)

Photo: Sue Ogrocki, Associated Press

John Warner surveys the damage near a friend's mobile home in... Photo-4656384.62754 - Houston Chronicle

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A smashed car sits in a debris field in the Rancho Brazos subdivision Sunday, May 19, 2013 in Granbury, Texas. Residents in the neighborhood continued cleanup of their damaged homes after a May 15 tornado wreaked havoc on the area, injuring dozens and killing six people. (AP Photo/The Dallas Morning News, G.J. McCarthy) less

A smashed car sits in a debris field in the Rancho Brazos subdivision Sunday, May 19, 2013 in Granbury, Texas. Residents in the neighborhood continued cleanup of their damaged homes after a May 15 tornado ... more

Photo: G.J. McCarthy, MBR

A smashed car sits in a debris field in the Rancho Brazos... Photo-4652759.62754 - Houston Chronicle